Overexpression of StDREB1 Transcription Factor Increases Tolerance to Salt in Transgenic Potato Plants

It has been established that drought-responsive element binding (DREB) proteins correspond to transcription factors which play important regulatory roles in plant response to abiotic and biotic stresses. In this study, a novel cDNA encoding DREB transcription factor, designated StDREB1, was isolated from potato (Solanum tuberosum L.). This protein was classified in the A-4 group of DREB subfamily based on multiple sequence alignments and phylogenetic characterization. Semi-quantitative RT-PCR showed that StDREB1 is expressed in leaves, stems, and roots under stress conditions and it is greatly induced by NaCl, drought, low temperature, and abscisic acid (ABA) treatments. Overexpression of StDREB1 cDNA in transgenic potato plants exhibited an improved salt and drought stress tolerance in comparison to the non-transformed controls. The enhanced stress tolerance may be associated with the increase in P5CS-RNA expression (delta (1)-pyrroline-5-carboxylate synthetase) and the subsequent accumulation of proline osmoprotectant in addition to a better control of water loss. Overexpression of StDREB1 also activated stress-responsive genes, such as those encoding calcium-dependent protein kinases (CDPKs), in transgenic potatoes under standard and high salt conditions. These data suggest that the StDREB1 transcription factor is involved in the regulation of salt stress tolerance in potato by the activation of different downstream gene expression.